The SIR provided [U-"C]Glucal While the role of carbohydrates is wall recognized in a variety of important biological phenomena, study of them has been restricted by availability of material. Recent advances in carbohydrate chemistry, including development of solid phase synthesis methods have helped address this limitation, offering general protocols for preparing significant quantities of well defined pure material. Such approaches have already bom fruit in the preparation of members of the Lewis blood group carbohydrates. Expression and recognition of these carbohydrates have been associated with cellular recognition, bacterial infection and cancer, making these interesing targets for conformational analysis to understand their biological roles. Investigations of solution conformation of the Lewis x determinant have been undertaken using proton NMR and heteronuclear NMR at natural abundance. In one instance, the C l' of one of the sugars in tLewis x oligosaccharide was labeled with 13C, providing advantages for conformational analysis. In gerneral experimental data for conformational analysis has been insuffcient to fully define the structure and analysis has relied heavily on modeling. The aim of preparing the labeled compounds proposed here is to overcome these limitations byrnaking powerful heteronuclear NMR techniques availabe. An important aspect of the novel synthetic methods being developed is that they can be combined effectively with isotopic labeling. This will dramatically improve the NMR results and enhance the conformational analysis of these spedies. The impact of isotopic labeling on the study of RNA illustrates the kind of advantages that can be gained in studying sugar moieties.